1. Field of the Invention
The invention relates to a charge circuit/method and in particular to a charge circuit/method using charge current and voltage in pulses to charge batteries.
2. Related Art
Batteries of all shapes and sizes, available in sealed and maintenance-free products, are mass-produced today. Batteries are commonly used to provide a direct-current (dc) source of electrical energy in a wide variety of applications.
Battery charging is accomplished through delivery of an external power source to a battery, thereby ionizing the plates to opposing potentials (voltages or electrical pressures) and reversing the electrochemical process that occurs when the battery is used to supply energy to a load. Refer to FIG. 1 depicting a charge topology of half constant current. The voltage in the battery increases with time, while the charge current decreases gradually. Refer to FIG. 2 depicting a charge topology of constant current. In FIG. 2, the charge current remains constant during the whole charge.
Refer to FIG. 3 depicting a charge topology of constant current and current voltage. The topology in FIG. 3 is a multi-stage charge method, which may reduce the charge time. A multi-stage charger first applies a constant current charge, raising the cell voltage to a preset voltage. The battery is charged to such as 70% in stage 1. During the topping charge in stage 2 that follows, the charge current is gradually reduced as the cell is being saturated.
The charge method illustrated in FIG. 1˜3 may not fully charge the energy into the batteries. Further, the constant charge current in the conventional charge method is difficult to deliver into the battery continuously. For other batteries, like silicone power battery, the internal resistance of these batteries increases with the usage. Thus, charge energy into the batteries becomes more and more difficult. Besides, the ageing of batteries also arise difficulty of charge.
For some large capacity batteries, charge and discharge of the power source to and from batteries is done by chemical reaction. Some production is generated during the chemical reaction process. In these batteries, lead-acid batteries may be assembled to provide the greatest energy density, and have the longest life cycle. In lead acid batteries, the reaction of lead and lead oxide with the sulfuric acid electrolyte produces a voltage. The supplying of energy to and external resistance discharges the battery. Lead Sulfate is generated in the charge and discharge process for lead acid batteries. Lead Sulfate not only results in unfull charge of the batteries, but also decrease of life-span.